1. Field of the Invention
The present invention relates to an apparatus and a method for trimming a side of a steel plate before a process of rolling and after a process of annealing the steel plate.
2. Discussion of Related Art
A process of trimming a side of a steel plate refers to a process of trimming a side portion of a steel plate before rolling in a continuous cold rolling process for the steel plate and is performed to remove cracks in an edge portion of a hot rolled plate, which cause fractures of a plate during the rolling, and other flaws. Also, a process of trimming a side of a steel plate refers to a process of trimming a side portion of a steel plate to adjust the width of the plate after annealing process.
FIG. 1 illustrates a side trimming apparatus having a typical structure. FIG. 2 illustrates a side-trimming mechanism of a steel plate using the side trimming apparatus of FIG. 1.
As shown in FIG. 1, the side trimming apparatus includes rotating knives 1 and 2 disposed above and below and cut an edge portion of the steel plate. The rotating knives 1 and 2 have a disc shape and are configured to rotate according to the movement of a steel plate S. A horizontal clearance a and a vertical clearance b are formed between the knife 1 located above and the knife 2. Here, the horizontal clearance a means a gap between the rotating knives 1 and 2 in a horizontal direction and the vertical clearance b means a lap where the rotating knives 1 and 2 overlap with each other in a vertical direction.
The steel plate S is cut at the edge portion by a certain amount while sequentially passing through the rotating knives 1 and 2 having the horizontal and vertical clearances a and b. Here, the rotating knives 1 and 2 do not have a self driving force and are rotated by a force due to the movement of a steel plate S.
As shown in FIG. 2, the edge portion of the steel plate S is cut by shearing and tearing by the upper and lower knives 1 and 2. First, the rotating knives 1 and 2 shear the steel plate S by as much as a set amount of the vertical clearance b. Also, due to rotating forces of the rotating knives 1 and 2, cracks C occur at sheared end portions, that is, end portions where the rotating knives 1 and 2 penetrate. As described above, each of the cracks C which occur at the end portions of the rotating knives 1 and 2 grow to meet each other at a center of a cut surface of the steel plate S, and the edge portion is finally cut.
As described above, as a pair of such rotating knives 1 and 2 pressurize to an upper surface and a lower surface of the steel plate S, the side-trimming of the steel plate is performed by a shearing and breaking mechanism. When a steel plate being transferred at a high speed is consecutively sheared using the mechanism, continuous pressures and mechanical impacts are applied to the edge portions of the rotating knives 1 and 2, thereby generating wear and damage. Accordingly, when the rotating knives 1 and 2 are used for a certain period, the rotating knives 1 and 2 may be replaced or may be reused after a polishing operation.
Recently, in a cold rolling process, production of advanced high strength steel (AHSS) is on an upward tendency and AHSS with improved strength is continually being developed. As described above, as the strength of the steel plate increases, necessarily causing wear and damage to the rotating knives 1 and 2. Due to the wear of the rotating knives 1 and 2, flaws such as cracks or burrs may be generated. When the rotating knives 1 and 2 are worn out or damaged, it is necessary to stop a continuous process to replace the rotating knives 1 and 2, thereby lowering production speed.
To overcome the wear and damages of the rotating knives 1 and 2 described above, currently, side trimming is performed while lowering a transfer speed of the steel plate. However, since the whole production speed in the continuous process is lowered, the reduction of the transfer speed cannot be a fundamental solution. In addition, in the case of AHSS having strength at a certain level or more, the rotating knives 1 and 2 are too easily damaged to perform side trimming.
Additionally, even though the strength of the rotating knives 1 and 2 has been increased by changing material as another solution to prevent the rotating knives 1 and 2 from being damaged, trimming AHSS being transferred at high speed remains limited.